[ntp:questions] question on leap second insertion in syslog

Martin Burnicki martin.burnicki at meinberg.de
Thu Feb 26 11:00:33 UTC 2009


Manikandan D wrote:
> Hello to the great brainy(s) out there..
> Quick question about the logging of leap second in the syslog... we have
> few number of Linux boxes, last year December 2008 23:59:59 when there was
> a leap second inserted, all the systems reported "Clock: inserting leap
> second..."

If the kernel supports leap seconds (this is the case for Linux) then the
NTP daemon just passes the leap second announcement to the kernel. The
kernel then handles the leap second and generates the appropriate log

> But in our local testing for leap second inserting we noticed that the
> syslog reported "discipline status change 0010" at times "discipline
> status change 0011"
> Can someone please explain me the difference here? I understand there are
> no issues, but for documenting purpose I need the information, your inputs
> will be highly appreciated..

The NTP daemon does a plausibility check, i.e. it accepts leap seconds only
at the end of June or December. 

>From what you've written above it looks like you have chosen some other date
to test a leap second. In this case ntpd does not pass the leap second
announcement to the kernel. Instead, if ntpd's configured time source
inserts a leap second at a non-supported date then ntpd will observe a
sudden time step of 1 second, and will step the system time some time
later, which may result in the status change you've observed (I haven't
checked the meaning of the status codes, though).

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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